Apart from Sandbagger's Tally-ho!, there were once many EAW websites, sources of additional 1.2x planes and skins and other addons. Many have now disappeared.
But some remain, probably more by oversight than design.
These are the ones I could find:
Jan Tuma`s (old) EAW Page:
http://eaw.wz.cz/index2.html Many models and skins and add-ons relating to the Eastern Front
Jan Tuma`s EAW Cold-War Pages
http://tumajan.sweb.cz/ One of Jan's uncompleted projects
Alain James' Check Six:
http://alainjames.free.fr/Skins.htm Nice skin collection by Alain and others
Alessandro Borges' Aces Over Gyn
http://www.geocities.ws/alessandroborges/index.htm Skins, terrains, scenarios, and utilities
Jason and Steve's Flight Sim Site:
http://www.trats1.freeuk.com/ Skins, sounds and skies
Pisis' EAW Page:
http://pisis.eaw.page.sweb.cz/menu.htm Skins and screens with an emphasis on Czech pilots
Fabio Mele EAW SKINS:
http://www.eaw.it/ Skins and screens with an emphasis on Italian planes
Capitán Manduca's EAW Workshop:
http://capitan.manduca.free.fr/ Unfortunately the skins downloads are not working, but there are other things.
Just a reminder that the files on these sites are 1.2x, so useful in original Microprose 1.2, GOG 1.28, Code Group 1.28C. The planes and skins can be used in 1.2E and 1.29. Those working 1.6 may find things that can be converted to use in that setup.
If anyone knows of any others, please post.